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Thermostat switching circuitry robust against anomalous HVAC control line conditions

  • US 9,612,031 B2
  • Filed: 01/07/2015
  • Issued: 04/04/2017
  • Est. Priority Date: 01/07/2015
  • Status: Active Grant
First Claim
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1. A thermostat comprising:

  • a plurality of HVAC wire connectors configured to receive a plurality of HVAC wires from an HVAC system, the plurality of HVAC wire connectors comprising at least one call relay wire connector and at least one power return wire connector;

    one or more solid-state switching elements coupled to the at least one call relay wire connector and the at least one power return wire connector, the one or more solid-state switching elements having a first operating state in which the one or more solid-state switching elements create a connection between the at least one call relay wire connector and the at least one power return wire connector, the one or more solid-state switching elements also having a second operating state in which said connection between the at least one call relay wire connector and the at least one power return wire connector is interrupted;

    power monitoring circuitry coupled to the one or more solid-state switching elements that measures voltage and/or current characteristics of the one or more solid-state switching elements during times when the one or more solid-state switching elements are operating in the first operating state;

    processing and control circuitry coupled to the power monitoring circuitry and configured to control at least one HVAC function associated with the at least one call relay wire connector, wherein the processing and control circuitry is further configured to;

    cause the one or more solid-state switching elements to operate in the first operating state to actuate the at least one HVAC function;

    during times when the at least one HVAC function is actuated, detect an anomaly associated with the voltage and/or current measurements from the power monitoring circuitry;

    in response to detecting the anomaly, cause the one or more solid-state switching elements to operate in the second operating state for at least a first time interval;

    after the expiration of the first time interval, cause the one or more solid-state switching elements to operate in the first operating state and determine whether the anomaly is still present.

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